Variable disk capacitor



Sept. 28, 1965 MA'IQ'SUJIRO MASUl VARIABLE DISK CAPAC ITOR OriginalFiled March 17. 1959 FIG. I

HllilllllllllllllllllllllllilllllllllllllllllflllfllllflfllllilllllllllI M mm Wm s. E 0N N M M 0 4 m .w s 1 M United States Patent 3,209,219VARIABLE DISK CAPACITOR Matsujiro Masui, Nishinomiya-shi, Japan,assignor to Matsushita Electric Industrial Co., Ltd., Osaka, JapanOriginal application Mar. 17, 1959, Ser. No. 799,971. 5 Divided and thisapplication May 27, 1963, Ser. No. 283,295 Claims priority, applicationJapan, Mar. 25, 1958, 33/ 14,961; Apr. 3, 1958, 33/ 16,951; Apr. 4,1958, 33/17,127, 33/17,128, 33/17,129; June 14, 1958, 33/30,339; June16, 1958, 33/30,783, 33/30,784, 33/300,785; July 16, 1958, 33/256,677,33/136,678, 33/36,679, 33/36,680; Dec. 19, 1958, 33/67,522, 33/ 67,527;Feb. 12, 1959, 34/ 7,721; Feb. 23, 1959, 34/ 10,100

4 Claims. (Cl. 317-254) This application is a division of Serial No.799,971, filed March 17, 1959, and now abandoned.

The present invention relates to a variable capacitor and particularlyto a variable capacitor especially suitable for use in small-sized radioreceiving sets.

The present invention is intended to provide a novel and improved highperformance variable capacitor which has a large and stable capacitycapable of fine adjustment and complies with the recent trend of radioreceiving sets toward smaller sizes.

A further object of the present invention is to provide a variablecapacitor having a large capacity relative to its dimensions in whichrotary and stationary electrode plates are spaced apart from each otherby a layer or layers of solid dielectric material alone thereby toincrease the dielectric constant of the capacitor.

Another object of the present invention is to provide a variablecapacitor in which many of essential component parts each serve aplurality of purposes and which is easy to manufacture, rugged inconstruction, and highly durable.

These and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofsome embodiments of the invention.

According to the present invention, there is provided a variablecapacitor which has an inner electrode element and a pair or outerelectrode elements respectively disposed on opposite sides of said innerelectrode element, 4 all of said electrode elements being relativelyrotatably pressed together with solid dielectric layers interposedbetween said inner electrode element and said outer electrode elementsin such manner as to provide a capacity variable with relative angularmovement of said inner and outer electrode elements.

According also to the invention there is provided a variable capacitorof the kind described in which an inner electrode element is rotatableand a pair of outer electrode elements are stationary.

According also to the present invention, a variable capacitor comprisesa casing tightly enclosing an assembly of a rotary electrode disc and apair of stationary electrode discs disposed on opposite sides of saidrotary elec trode disc. 60

According to a further feature of the invention, a recess is formed in awall of the casing of the variable capacitor for providing stop meansfor limiting the movement of a lug extending from the rotatable shaftcarrying the rotary electrode disc. 65

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription taken in connection with the accompanying drawings whichillustrate several embodiments, chosen by way of example, of thevariable capacitor according to the invention, and in which:

FIGURE 1 is a longitudinal cross sectional view of Patented Sept. 28,1965 Ice a cylindrical variable capacitor according to the presentinvention, illustrating the basic structure thereof; and

FIGURE 2 is an exploded perspective view of component parts 'of thevariable capacitor shown in FIGURE 1.

Referring now to the figures illustrating a preferred embodiment of thepresent invention, reference numeral 41 designates a casing for thevariable capacitor which is of insulating material and has a circularinner wall 42 defining a recess 43 for accommodating an electrodeassembly. At the bottom of this recess 43 a semicircular cavity 46 isformedin the inside surface of end wall 46a. A stop lug projectsradially from one end of a rotatable shaft 44 and engages in said recess36, moving from one end of the recess to the other so as to limitrotation of shaft 44 within a predetermined angular range, in thisinstance 180. Firmly secured to the rotatable shaft 44 is a rotary disc49 comprising an insulating plate 47 with a pair of semicircularelectrode discs 48-48 adhered or otherwise joined to opposite surfacesof said plate 47 and in electrical connection with a contact means (notshown) through shaft 44. A pair of stationary discs 50-50 are arrangedso as to embrace this rotary disc therebetween. Each of the stationarydiscs 50-50 comprises a dielectric insulating plate 51 made of titaniumoxide having a semicircular metal sheet 52 coated on the back thereof.The stationary disc 50 has a segment removed therefrom to form a fiat 53formed on the periphery thereof for cooperating with a fixing element 54in the form of a rectangular plate which is inserted into a spacedefined by said flat 53 of the stationary disc 50 and the inner wall 42of the recess 43 formed in the casing 41, thereby firmly securing thestationary disc 50 relative to the casing 41. The inner wall can haveformed therein a slot 55 for further ensuring the retention of saidfixing element 54. Bearing against the back of each of the stationarydiscs is a resilient plate 56 for pressing the discs against the rotarydisc. A washer 57 is provided between each resilient plate 56 and thecasing 41. The rotary disc 49, stationary discs 50-50, resilient plates4646, and washers 57-57 are all accommodated in the recess 43 in thecasing 41, and tightly enclosed by a closure member 58. The closure 58is secured to the casing by screws 59, which can also serve as electrodeterminals by electrically connecting them by means of internallythreaded inserts 60 embedded in the casing 41 to the stationary discs50. Thus, the stationary discs 50 can be connected in a circuit so as tobe of one polarity and the movable discs can be connected so as to be ofthe other polarity.

According to the present invention, the stationary discs 50-50 may befixed to the casing 41 by interposing a fixing element 54 between flat53 formed on the periphery of the stationary disc 50 and the inner wall42 of the recess 43 formed in the housing 41 for accommodating theelectrode assembly, as described hereinbefore. Various fixing elements54 of different thicknesses can be made available so that a fixingelement of any desired thickness may be selectively used to firmlysecure the respective stationary discs 50-50. The assembling operationof the variable capacitor is thereby greatly facilitated, and further,the stationary discs can be easily fixed in a predetermined angularposition. In such construction, the stationary disc are prevented frombeing damaged even where they are made of brittle material such astitanium oxide. It will be appreciated that such structure is veryuseful from a practical standpoint in that it makes it possible to makethe variable capacitor in small sizes.

It is thought that the invention and its advantages will be understoodfrom the foregoing description and it is apparent that various changesmay be made in the form, construction and arrangement of the partswithout departing from the spirit and scope of the invention orsacrificing its material advantages, the form hereinbefore described andillustrated in the drawings being merely a preferred embodiment thereof.

What I claim is:

1. A variable capacitor comprising a rotatable shaft, a rotary dischaving electrode members of one polarity on opposite sides of saidrotary disc, said rotary disc being secured to said rotatable shaft, apair of stationary electrode discs of the other polarity respectivelydisposed on opposite sides of said rotary electrode disc, a layer ofsolid dielectric material on the surface of each of said stationaryelectrode discs, a pair of resilient plates respectively disposed on thesides of said stationary discs remote from said rotary disc, a casing ofnon-conductive material tightly enclosing said rotary electrode disc,said pair of stationary electrode discs, and said resilient discs, saidcasing having a bottom portion in which one end of said rotatable shaftis rotatably mounted, said bottom portion having a cavity thereinopening into the interior of said casing, and lug means rigidly mountedon said shaft and extending radially of said shaft and being located insaid cavity and movable therein from one end of All the cavity to theother so that the rotation of the shaft is limited by said lug abuttingagainst the opposite ends of said cavity.

2. A variable capacitor as claimed in claim 1 in which said cavity issemicircular.

3. A variable capacitor as claimed in claim 1 in which said stationaryelectrode discs have a flat edge thereon, and a fixing element betweensaid flat edges and the inside wall of the interior of said casing andholding said stationary discs against rotation within the casing.

4. A variable capacitor as claimed in claim 1 in which said casing has arecess in the inside wall of the interior thereof in which said fixingelement is positioned to hold it against movement.

References Cited by the Examiner UNITED STATES PATENTS 1,572,504 2/26Perlesz 3 1725 3 2,913,645 11/59 Hansen 317249 FOREIGN PATENTS 256,1672/ 27 Great Britain.

JOHN F. BURNS, Primary Examiner.

1. A VARIABLE CAPACITOR COMPRISING A ROTATABLE SHAFT, A ROTARY DISCHAVING ELECTRODE MEMBERS OF ONE POLARITY ON OPPOSITE SIDES OF SAIDROTARY DISC, SAID ROTARY DISC BEING SECURED TO SAID ROTATABLE SHAFT, APAIR OF STATIONARY ELECTRODE DISCS OF THE OTHER POLARITY RESPECTIVELYDISPOSED ON OPPOSITE SIDES OF SAID ROTARY ELECTRODE DISC, A LAYER OFSOLID DIELECTRIC MATERIAL ON THE SURFACE OF EACH OF SAID STATIONARYELECTRODE DISCS, A PAIR OF RESILIENT PLATES RESPECTIVELY DISPOSED ON THESIDES OF SAID STATIONARY DISCS REMOTE FROM SAID ROTARY DISC, A CASING OFNON-CONDUCTIVE MATERIAL TIGHTLY ENCLOSING SAID ROTARY ELECTRODE DISC,SAID PAIR OF STATIONARY ELECTRODE DISCS, AND SAID RESILIENT DISCS, SAIDCASING HAVING A BOTTOM PORTION IN WHICH ONE END OF SAID ROTATABLE SHAFTIS ROTATABLY MOUNTED, SAID BOTTOM PORTION HAVING A CAVITY THEREINOPENING INTO THE INTERIOR OF SAID CASING, AND LUG MEANS RIGIDLY MOUNTEDON SAID SHAFT AND EXTENDING RADIALLY OF SAID SHAFT AND BEING LOCATED INSAID CAVITY AND MOVABLE THREIN FROM ONE END OF THE CAVITY TO THE OTHERSO THAT THE ROTATION OF THE SHAFT IS LIMITED BY SAID LUG ABUTTINGAGAINST THE OPPOSITE ENDS OF SAID CAVITY.